As an American expatriate in Buenos Aires, Mei-Ling Hopgood noticed right away how late Argentine babies stayed up - or, if they weren’t exactly up, were asleep in someone’s arms or on two restaurant chairs pushed together while their parents enjoyed traditional late dinners out. After having her own daughter in 2007, she wondered whose child-rearing advice to follow: the schedule-driven American paradigm or the child-doting, late-night socializing ethos in Argentina. Pondering such cultural differences led her on a quest to chronicle and understand different ways of bringing up baby. Along the way, Hopgood examines Kenyan mothers wearing sling-wrapped infants, Chinese moms whose toddlers wear split-bottom trousers to avoid diapering, and Mayan families whose smallest members work alongside their parents.

Hopgood, an adopted American who has reconnected with her biological family in Taiwan and is raising her daughters in a bilingual, multicultural household, writes from a place of respectful, cosmopolitan curiosity - a refreshing break from the often judgmental tone of parenting books and blogs. If there’s any overarching lesson here, it’s that “there are many ways to be a good parent in the world.’’ Readers might pick up another, unstated theme: Many other cultures seem to provide more nurturing in infancy (they believe one must “let babies be babies’’) and higher expectations (of work, independent play, self-regulation) in childhood. But Hopgood doesn’t pursue this or any other idea particularly rigorously. Another weakness: her repeated reference to fathers who “babysit’’ their children. Still, the book is breezy and entertaining, and Hopgood is charmingly self-deprecating about her own mothering of the formidable Sofia, who emerges as a sassy character in her own right.

THE NIGHT SWIMMER

By Matt Bondurant

Scribner, 274 pp., $25

Courtesy of a contest staged by a liquor company, American couple Fred and Elly Bulkington win a pub in a coastal Irish village. At first, the glorious cliffs and ocean views, not to mention the musical Irish still spoken by many locals, seem to Elly the ingredients of a fantastic adventure. An open-water swimmer, she literally dives in, training for a dangerous swim between the tiny nearby island and its storm-ravaged lighthouse. But in this eerie novel by Matt Bondurant, his third, it’s not long before everything about Fred and Elly’s life turns dark and stormy.

While the story’s broad strokes are almost sociological - conflicts over land and corruption, organic farmers vs. local machine politicians - the details move with the weirdness of magical realism. There’s the ghostly child Elly sees clinging to the lighthouse, as well as a shadowy armless figure who appears to be watching her from across a desolate field; both ultimately lead back to earthly explanations, but the mood they cast is creepy and discomfiting. Bondurant’s equally strong at constructing an emotional landscape: the fraught, error-prone conversations between spouses afraid of losing their marriage, Elly’s clear-eyed descriptions of their shared interest in both the writers and the cocktails of the American midcentury. Parties they hosted would break up early, “and then it would be ten o’clock and Fred and I standing in our empty kitchen, a half pitcher of martinis left, shouting at each other.’’

IN OUR PRIME: The Invention of Middle Age

By Patricia Cohen

Scribner, 306 pp., illustrated, $25

At what age do you consider yourself middle-aged? In this brilliant, wide-ranging book, which its author calls “a biography of the idea of middle age,’’ one persistent theme is that the very definition of middle age, or midlife, is a moving target. All life stages are man-made, Patricia Cohen points out, and both specific categories and the broad ideas behind them are subject to influence by social, economic, scientific, philosophical, and aesthetic trends. “A successful midlife has become equated with an imitation of youth,’’ a fact anyone with a television can confirm, but how we reached this point is a story packed with surprising twists, masterfully told.

The idea of middle age only took hold in the middle of the 19th century, she writes, a product not of increased life span (statistics regarding an average death age in the mid-40s, which persisted until the turn of the 20th century, reflect very high rates of infant and child mortality - as Cohen points out, people who made it past 15 had a good chance of reaching 60 and beyond), but of changes in the industrial economy, shifting rural-to-urban demographics, and women’s ability to have fewer children. By the early 1900s, age had become “a handy yardstick’’ used by schools, scientists, and a burgeoning media and advertising complex. One scientific management expert proclaimed that “[t]he year of maximum productiveness is thirty-nine’’ (unsurprisingly, the growing emphasis on age groups led to more people lying about their ages on the Census). After a brief flourishing of middle age as a kind of haven for women - Cohen cites such turn-of-the century actresses as Lillie Langtry as mature beauty ideals - a cult of youth took hold that has never really left. It wasn’t long before, as today’s pharmaceutical and cosmetic landscape reminds us, “the very process of aging was seen as abnormal.’’ Despite the often-infuriating aspects of what she chronicles, Cohen’s lively prose and thoughtful insights make this a joy to read.

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